飛騨古川〜御母衣湖地域の濃飛流紋岩(概報) : 濃飛岩体北部地域における東西地質断面

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The Nohi Rhyolite is a large Cretaceous to Paleogene volcanic pile distributed extensively in central Japan and consisting chiefly of silicic pyroclastic flow deposits, mainly welded tuffs. Its northern part (Hida-Furukawa-Miboro-Lake area) has been studied both stratigraphically and volcanologically. Stratigraphic succession of the rhyolite in this part is grouped roughly into three volcanic stages (Stage Ia, Ib and II), as shown in the following table. [Table] The Sujikawa-dani and the Ohara-dani Welded Tuffs belonging to the Stage Ia filled up the depressionon the basement rocks such as the lower Cretaceous system (Tetori Group), diorite (Kitamata-dani Diorite) and granites (Akimachi and Hikodani Granites), in the western part of the studied area. In the Stage Ib, the basin migrated westwards because of the upheaval in the easternpart, but after that, it was filled up by the Oshirakawa Formation, which consists of lacustrine deposits, sillicic pyroclastic rocks and lavas, and intermediate to mafic lavas and pyroclastic rocks. In the upheaved area, local subsidence took place accompanied by the eruption of rhyolite lavas (Odori-gawa Formation) and the deposition of sillicic pyroclastic materials (Nihon-gi Formation). After the short time erosion, violent volcanism of the Stage II began with the subsidence in the eastern part of the studied area. It was followed by the sedimentation of nonsorted very coarse-grained deposits (Sumi-toge Formation), and succeeded by the deposition of enormous amounts of pyroclastic flow deposits (Hikodani, Sotsui-dani and Tonokawa Welded Tuffs). Finally, the western and eastern magins were intruded by the stocks of granodiorite porphyry and granite porphyry, respectively, which are supposed to be co-magmatic with the volcanics of the Stage II.
日本地質学会の論文
1979-09-20

飛騨古川〜御母衣湖地域の濃飛流紋岩(概報) : 濃飛岩体北部地域における東西地質断面

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